1. Field of the Invention
The present invention relates to an image-capturing device and an in-vehicle camera.
2. Description of the Related Art
An image-capturing device into which an imaging optical system and an imaging element such as a CCD image sensor are built, besides being used in a digital still camera or the like, has recently been used as well in an in-vehicle camera such as a back monitor camera (a rear view camera, a rear view monitor).
In such an imaging-capturing device, if positions of the imaging element and the imaging optical system which are positioning-adjusted with high accuracy shift, a focus position shifts and it is impossible to obtain a high-quality (clear) image. Therefore, especially in an in-vehicle camera, it is necessary to affix strongly so that the imaging element and the imaging optical system do not shift from their positions after being positioning-adjusted, to always obtain a high-quality image even under a driving environment where vibration and heat are applied, or under a hot environment such as summer.
In general, a method of bonding or a method of screw-fastening is used to adjust positions of the imaging element and the imaging optical system with high accuracy and fixing the positions strongly. However, anchorage strength equal to or more than that of the screw-fastening cannot be obtained by only bonding. Moreover, in the method by only screw-fastening, because the positioning adjustment is limited by a pitch of the screw or a position of a hole, the positioning adjustment cannot be performed with high accuracy.
Thus, a positioning fixation structure combining these two methods has been made (for example, refer to JP H09-54233 A). In JP H09-54233 A, an optical module which projects light emitted from an optical element through an optical component such as a lens has a first member which retains the optical element and a second member which retains the optical component, the first and second members are temporarily positioned through an adhesive (an elastic body) lying between them, and then an interval between the first and second members is set by a screw (an interval setting part) under a state where the adhesive is compressed, and the positioning adjustment of the optical element and the optical component (the lens) is carried out.
However, the following problems arise in the positioning adjustment described in JP H09-54233 A.
Accuracy is limited by the pitch of the screw, due to the positioning adjustment being performed with the screw. That is to say, it is impossible to freely adjust the position of the first member which retains the optical element with a device different from that for positioning adjustment of the optical module, and an accurate adjustment higher than that of the method by bonding can not be achieved. For example, when the pitch of the screw is 0.5, and its accuracy is 1/10, i.e., 0.05 mm, and the accuracy of adjustment varies depending on a screw chosen, or how finely the screw is capable of turning.
In addition, when a plurality of screws are tightened, tightening of the screws has to be carried out while performing adjustment for each screw, a position of a substrate adjusted with high accuracy shifts by differences when tightening or positioning the screw.
Moreover, when an optical axis of the optical component (the lens) is set to be in a vertical direction, an adjustment in a horizontal direction perpendicular to the vertical direction is essentially determined by the position of the screw hole, and the degree of freedom of adjustment is minimal.
In addition, when temporary positioning is carried out with the adhesive (the elastic body), a following process in which the positions of the optical element and the optical component (the lens) are adjusted accurately by the screw is preliminarily assumed. That is, two adjustments of positioning are necessary, which takes time to perform.
Thus, even if such a positioning adjustment described in JP H09-54233 A is applied to a positioning adjustment of the imaging element and the imaging optical system, the positions of the imaging element and the imaging optical system can not be strongly fixed under a state where the positions of the imaging element and the imaging optical system have been adjusted with high accuracy, and a stable and high-quality image cannot be obtained, due to the above-mentioned problems.